The invention relates to a pickup head (hereinafter referred as PUH) tilt control method, and more particular to a PUH tilt control method for calibrating the tilt control value in real time.
FIGS. 1A to 1E are schematic illustrations showing the relative relationships between the optical disk, PUH, and spindle motor.
FIG. 1A shows the schematic illustration that the optical disk is not curved and perpendicular to the laser beam of the PUH. That is, the optical disk 11A is not curved and perpendicular to the laser beam of the PUH 12A. In this ideal state, the optical disk drive (not shown) can read the data all over the optical disk 11A without additionally controlling the tilt angle of the PUH 12A.
FIG. 1B shows the schematic illustration that the optical disk is not curved and is disposed horizontally but the laser beam of the PUH 12B is not perpendicular to the optical disk 11B. In this state, the optical disk drive only has to calibrate the PUH tilt once when the optical disk 11B is placed into the optical disk drive, and then the same calibration value is used to control the tilt of the PUH 12B to read the data all over the optical disk 11B.
FIG. 1C shows the schematic illustration that an optical disk tray is not perpendicular to the laser beam of the PUH. That is, the optical disk tray 13C is not perpendicular to the PUH 12C. Therefore, the laser beam is also not perpendicular to the optical disk 11C. In this state, the optical disk drive only also has to calibrate the PUH tilt once after the optical disk 11C is placed into the optical disk drive, and then the same calibration value is used to control the tilt of the PUH 12C to read the data all over the optical disk 11C.
FIG. 1D shows the schematic illustration that the outer side of the optical disk is curved. That is, the optical disk 11D is bent into a monotone curve such that the relative angle between the laser beam of the PUH 12D and the optical disk 11D is not fixed but ascends or descends with the position. In this state, the optical disk drive can calibrate the PUH tilts at the inner track and outer track when the optical disk 11D is placed into the optical disk drive. Then, the interpolation method or other methods may be used to calculate the tilt control values of other tracks according to the tilt control values of the inner and outer tracks. Thus, the PUH tilt may be controlled using the calculated tilt control values in different tracks so that the data all over the optical disk 11D may be read.
FIG. 1E shows a state of an irregularly deformed optical disk, wherein the relative angle between the laser beam of the PUH 12E and the optical disk 11E is not fixed and has no fixed rule. In addition, because the calibrating tilt control value consumed much of time for one position and the time of starting process after a optical disk is placed into the optical disk drive is restricted within a predetermined time, the tilt control values of too-many positions cannot be calibrated at the starting process. Typically, only the tilt control values of the inner and outer tracks are calibrated.
Thus, in the state of FIG. 1E, the optical disk drive cannot utilize the conventional method to control the tilt angle of the PUH. So, the data of the optical disk drive cannot be correctly acquired when the optical disk is retrieved.